How to declare special XML schema (XSD) case

<x>stuff</x>
<y>stuff</y>
<x>stuff</x>

<y>stuff</y>
<x>stuff</x>
<x>stuff</x>

<x>stuff</x>
<x>stuff</x>
<y>stuff</y>
<x>stuff</x>

<xs:complexType name="myComplexType">
	<xs:sequence>
		<xs:element name="x" type="xs:string" minOccurs="0" maxOccurs="unbounded"/>
		<xs:sequence minOccurs="0">
			<xs:element name="y" type="xs:string"/>
			<xs:element name="x" type="xs:string" minOccurs="0" maxOccurs="unbounded"/>
		</xs:sequence>
	</xs:sequence>
    </xs:complexType>

<xs:complexType name="myComplexType">
  <xs:all>
    <xs:element name="x" type="xs:string" maxOccurs="unbounded"/>
    <xs:element name="y" type="xs:string" maxOccurs="1"/>
  </xs:all>
</xs:complexType>

<xsd:element name="parent">
  <xsd:complexType>
    <xsd:choice maxOccurs="unbounded">
      <xsd:element name="x" type="xs:string"/>
      <xsd:sequence>
        <xsd:element name="y" type="xsd:string" />
        <xsd:element name="x" type="xsd:string" />
      </xsd:sequence>
    </xsd:choice>
  </xsd:complexType>
</xsd:element>

<xs:element name="x" type="xs:string" minOccurs="0" maxOccurs="unbounded"/>
<xs:element name="y" type="xs:string" minOccurs="0" maxOccurs="1"/>
<xs:element name="x" type="xs:string" minOccurs="0" maxOccurs="unbounded"/>